Metric Collection and Calculation on C5 and
M5 Instances

Because C5 and M5 instances use the Nitro hypervisor, they publish CloudWatch metrics
differently than other instances, which use a Xen-based hypervisor. For more information,
see Nitro Hypervisor.

In basic monitoring for EC2 instances, seven pre-selected metrics are available at
the
five-minute frequency. When you use basic monitoring on any type of EC2 instance (using
either hypervisor), the hypervisor measures five separate samples per metric during
each
five-minute interval. The way that these data points are published to CloudWatch depends
on the
type of hypervisor used by the instance.

On Xen instances, these five samples are aggregated and reported to CloudWatch as
a single
data point at the end of the five-minute interval, with a time stamp corresponding
to
the beginning of the five-minute interval. The statistic set for this data point
includes a SampleCount of 5.

On Nitro instances, the data point is published to CloudWatch immediately after the
first
sample is taken during the interval. When each subsequent sample within the interval
occurs, the statistic set for that data point is updated to reflect all the samples
taken so far, but the time stamp remains the same. If you are graphing or monitoring
the
data as it is reported, the statistics for the current data point can appear to change
as each sample is taken during the five-minute interval. Each of the five samples
taken
during the interval are included in the SampleCount statistic.

Time

1:01PM

1:02PM

1:03PM

1:04PM

1:05PM

Sample Value

10

15

10

5

10

Published on Xen instances
(with basic monitoring enabled)

Nothing yet

Nothing yet

Nothing yet

Nothing yet

Average=10

Sum=50

Minimum=5

Maximum=15

SampleCount=5

Timestamp=1:00PM

Published on Nitro instances (with basic monitoring enabled)

Average=10

Sum=10

Minimum=10

Maximum=10

SampleCount=1

Timestamp=1:00PM

Average=12.5

Sum=25

Minimum=10

Maximum=15

SampleCount=2

Timestamp=1:00PM

Average=11.666

Sum=35

Minimum=10

Maximum=15

SampleCount=3

Timestamp=1:00PM

Average=10

Sum=40

Minimum=5

Maximum=15

SampleCount=4

Timestamp=1:00PM

Average=10

Sum=50

Minimum=5

Maximum=15

SampleCount=5

Timestamp=1:00PM

In the example shown in the preceding table, basic monitoring is being used. A sample
is
taken each minute over a five-minute interval. On a Xen-based instance, nothing is
published
until the end of the five-minute interval. At this time (1:05PM), the five samples
are
aggregated and a single data point is written with a 1:00PM time stamp. This data
point has
a SampleCount of 5. This one data point contributes 50 to the
Sum statistic for the metric.

On a Nitro instance, the data point is first written to CloudWatch at 1:01PM with
a time
stamp of 1:00PM and a value of 10. At 1:02PM, the new sample of 15 causes the Average
of the
1:00PM data point to change to 12.5, the average of the two samples. This also changes
the
Maximum to 15. The time stamp of this data point remains 1:00PM. At 1:03PM, the data
point
Average changes to 11.6. Finally, after the last sample at 1:05PM, the Average returns
to
10. The final Average statistic of the data point is 10, but it has contributed 50
to the
Sum as this five-minute period includes a SampleCount of 5 and
each of the five samples is included in the Sum. The Minimum and
Maximum values reflect the highest and lowest values of the samples taken
during the interval.

Because of the way that Nitro instances collect and calculate the data, we recommend
that you only set alarms with at least two evaluation periods or require "M out of
N"
breaching periods, where M is at least 2. This is because on Nitro instances, a single
sample during one five-minute period can cause the data point to temporarily breach
the
threshold, even if subsequent samples in that period bring the final statistic set
of this data
point to within the threshold. This "mutable" data point in the current sample can
cause the
alarm to activate during the middle of the interval. For more information, see Evaluating an Alarm.

The AWS/EC2 namespace includes the following CPU credit metrics for your T2 instances.

Metric

Description

CPUCreditUsage

[T2 instances] The number of CPU credits spent by the instance for CPU
utilization. One CPU credit equals one vCPU running at 100% utilization
for one minute or an equivalent combination of vCPUs, utilization, and time
(for example, one vCPU running at 50% utilization for two minutes or two
vCPUs running at 25% utilization for two minutes).

CPU credit metrics are available at a five-minute frequency only. If you
specify a period greater than five minutes, use the Sum
statistic instead of the Average statistic.

Units: Credits (vCPU-minutes)

CPUCreditBalance

[T2 instances] The number of earned CPU credits that an instance has
accrued since it was launched or started. For T2 Standard, the
CPUCreditBalance also includes the number of launch
credits that have been accrued.

Credits are accrued in the credit balance after they are earned, and
removed from the credit balance when they are spent. The credit balance has
a maximum limit, determined by the instance size. Once the limit is reached,
any new credits that are earned are discarded. For T2 Standard, launch
credits do not count towards the limit.

The credits in the CPUCreditBalance are available for the
instance to spend to burst beyond its baseline CPU utilization.

When an instance is running, credits in the CPUCreditBalance
do not expire. When the instance stops, the CPUCreditBalance
does not persist, and all accrued credits are lost.

CPU credit metrics are available at a five-minute frequency only.

Units: Credits (vCPU-minutes)

CPUSurplusCreditBalance

[T2 Unlimited instances] The number of surplus credits that have been
spent by a T2 Unlimited instance when its CPUCreditBalance is
zero.

The CPUSurplusCreditBalance is paid down by earned CPU
credits. If the number of surplus credits exceeds the maximum number of
credits the instance can earn in a 24-hour period, the spent surplus credits
above the maximum incur an additional charge.

Units: Credits (vCPU-minutes)

CPUSurplusCreditsCharged

[T2 Unlimited instances] The number of spent surplus credits that are not
paid down by earned CPU credits, and thus incur an additional
charge.

Spent surplus credits are charged when any of the following occurs:

The spent surplus credits exceed the maximum number of credits the
instance can earn in a 24-hour period. Spent surplus credits above the
maximum are charged at the end of the hour.

The instance is stopped or terminated.

The instance is switched from Unlimited to Standard.

Units: Credits (vCPU-minutes)

The AWS/EC2 namespace includes the following instance metrics.

Metric

Description

CPUUtilization

The percentage of allocated EC2 compute units that are currently in use on the
instance. This metric identifies the processing power required to run an application
upon a selected instance.

To use the percentiles statistic, you must enable detailed monitoring.

Depending on the instance type, tools in your operating system can show a lower
percentage than CloudWatch when the instance is not allocated a full processor core.

Units: Percent

DiskReadOps

Completed read operations from all instance store volumes available to the instance
in a specified period of time.

To calculate the average I/O operations per second (IOPS) for the period, divide the
total operations in the period
by the number of seconds in that period.

Units: Count

DiskWriteOps

Completed write operations to all instance store volumes available to the instance
in a specified period of time.

To calculate the average I/O operations per second (IOPS) for the period, divide the
total operations in the period
by the number of seconds in that period.

Units: Count

DiskReadBytes

Bytes read from all instance store volumes available to the instance.

This metric is used to determine the volume of the data the application reads from
the hard disk of the
instance. This can be used to determine the speed of the application.

The number reported is the number of bytes received during the period. If you are
using basic (five-minute) monitoring,
you can divide this number by 300 to find Bytes/second. If you have detailed (one-minute)
monitoring, divide it by 60.

Units: Bytes

DiskWriteBytes

Bytes written to all instance store volumes available to the instance.

This metric is used to determine the volume of the data the application writes onto
the hard disk of the
instance. This can be used to determine the speed of the application.

The number reported is the number of bytes received during the period. If you are
using basic (five-minute) monitoring,
you can divide this number by 300 to find Bytes/second. If you have detailed (one-minute)
monitoring, divide it by 60.

Units: Bytes

NetworkIn

The number of bytes received on all network interfaces by the instance. This
metric identifies the volume of incoming network traffic to a
single instance.

The number reported is the number of bytes received during the period. If you are
using basic (five-minute) monitoring,
you can divide this number by 300 to find Bytes/second. If you have detailed (one-minute)
monitoring, divide it by 60.

Units: Bytes

NetworkOut

The number of bytes sent out on all network interfaces by the instance. This
metric identifies the volume of outgoing network traffic from a
single instance.

The number reported is the number of bytes sent during the period. If you are using
basic (five-minute) monitoring,
you can divide this number by 300 to find Bytes/second. If you have detailed (one-minute)
monitoring, divide it by 60.

Units: Bytes

NetworkPacketsIn

The number of packets received on all network interfaces by the instance. This
metric identifies the volume of incoming traffic in terms of the number of packets
on
a single instance. This metric is available for basic monitoring only.

Units: Count

Statistics: Minimum, Maximum, Average

NetworkPacketsOut

The number of packets sent out on all network interfaces by the instance. This
metric identifies the volume of outgoing traffic in terms of the number of packets
on
a single instance. This metric is available for basic monitoring only.

Units: Count

Statistics: Minimum, Maximum, Average

The AWS/EC2 namespace includes the following status checks metrics. By default, status check
metrics
are available at a 1-minute frequency at no charge. For a newly-launched instance,
status check metric data is only available
after the instance has completed the initialization state (within a few minutes of
the instance entering the
running state). For more information about EC2 status checks, see Status Checks For Your Instances.

Metric

Description

StatusCheckFailed

Reports whether the instance has passed both the instance status check and the system
status check in the last minute.

This metric can be either 0 (passed) or 1 (failed).

By default, this metric is available at a 1-minute frequency at no charge.

Units: Count

StatusCheckFailed_Instance

Reports whether the instance has passed the instance status check in the last minute.

This metric can be either 0 (passed) or 1 (failed).

By default, this metric is available at a 1-minute frequency at no charge.

Units: Count

StatusCheckFailed_System

Reports whether the instance has passed the system status check in the last minute.

This metric can be either 0 (passed) or 1 (failed).

By default, this metric is available at a 1-minute frequency at no charge.

Units: Count

Amazon CloudWatch data for a new EC2 instance typically becomes available within one
minute
of the end of the first period of time requested (the aggregation
period) in the query. You can set the period—the length of time over
which statistics are aggregated—with the Period parameter. For more information on
periods, see Periods.

You can use the currently available dimensions for EC2 instances (for example,
ImageId or InstanceType) to refine the metrics returned. For
information about the dimensions you can use with EC2, see Dimensions for Amazon EC2 Metrics.

The AWS/EC2 namespace includes the following Amazon EBS metrics
for your C5 and M5 instances.

Metric

Description

EBSReadOps

Completed read operations from all Amazon EBS volumes attached to the
instance in a specified period of time.

To calculate the average read I/O operations per second (Read IOPS)
for the period, divide the total operations in the period by the
number of seconds in that period. If you are using basic (five-minute)
monitoring, you can divide this number by 300 to calculate the Read IOPS.
If you have detailed (one-minute) monitoring, divide it by 60.

Unit: Count

EBSWriteOps

Completed write operations to all EBS
volumes attached to the instance in a specified period of time.

To calculate the average write I/O operations per second (Write IOPS)
for the period, divide the total operations in the
period by the number of seconds in that period. If you are using
basic (five-minute) monitoring, you can divide this number by 300 to
calculate the Write IOPS. If you have detailed (one-minute) monitoring,
divide it by 60.

Unit: Count

EBSReadBytes

Bytes read from all EBS volumes attached to the instance in a
specified period of time.

The number reported is the number of bytes read during the period.
If you are using basic (five-minute) monitoring, you can divide this
number by 300 to find Read Bytes/second. If you have detailed (one-minute) monitoring,
divide it by 60.

Unit: Bytes

EBSWriteBytes

Bytes written to all EBS volumes attached to the instance in a
specified period of time.

The number reported is the number of bytes written during the
period. If you are using basic (five-minute) monitoring, you can
divide this number by 300 to find Write Bytes/second. If you have
detailed (one-minute) monitoring, divide it by 60.

Unit: Bytes

EBSIOBalance%

Available only for the smaller C5 and M5 instance sizes. Provides information about
the percentage of I/O credits remaining in the burst bucket. This metric is available
for basic monitoring only.

The Sum statistic is not applicable to this metric.

Unit: Percent

EBSByteBalance%

Available only for the smaller C5 and M5 instance sizes. Provides information about
the percentage of throughput credits remaining in the burst bucket. This metric is
available for basic monitoring only.

The Sum statistic is not applicable to this metric.

Unit: Percent

Dimensions for Amazon EC2 Metrics

If you're using Detailed Monitoring, you can filter the EC2 instance data using any
of the dimensions in the following table.

Dimension

Description

AutoScalingGroupName

This dimension filters the data you request for all instances in a specified
capacity group. An Auto Scaling group is a collection of
instances you define if you're using Auto Scaling. This
dimension is available only for Amazon EC2 metrics when the instances are in such
an
Auto Scaling group. Available for instances with Detailed or Basic Monitoring enabled.

ImageId

This dimension filters the data you request for all instances running this Amazon
EC2
Amazon Machine Image (AMI). Available for instances with Detailed Monitoring enabled.

InstanceId

This dimension filters the data you request for the identified instance only.
This helps you pinpoint an exact instance from which to monitor data.

InstanceType

This dimension filters the data you request for all instances running with
this specified instance type. This helps you categorize your data by the
type of instance running. For example, you might compare data from an m1.small
instance and an m1.large instance to determine which has the better business
value for your application. Available for instances with Detailed Monitoring enabled.

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